The invention relates to the area of armor and in particular multilayer armor having a composite layer containing a first material, for example a ceramic, and a second material, such as a metal or metal alloy.
Ceramic has been known for its ballistic performance for a number of years, either as a material placed at the front face of a piece of armor or embedded in the metal material to increase overall armor effectiveness.
The most significant work in the area of cast composite armor has related mainly to production of armor with a series of ceramic reinforcements distributed in a metal matrix, generally obtained by a process related to casting.
These types of armor, although their performance is satisfactory, are generally difficult to fabricate and do not have guaranteed protection effectiveness that is identical for all angles of attack, for all impact points on the front face, and also have low performance with multiple impacts (two successive shots striking the same impact zone).
Moreover, in view of the nature and shape of the reinforcement bodies used, and in view of the implementation difficulties, the cost of the protection thus obtained is generally high by comparison to armor composed of monolithic materials.
Finally, the exceptional compressive strength performance of ceramics is not fully exploited due to the confinement configurations recommended by the various inventors, which do not exhibit an optimal configuration.
For example, McDougal et al., in their U.S. Pat. No. 3,705,558, provide a light armor composed of a layer of ceramic balls placed in contact but such that a small gap between the balls allows for a liquid metal coating to pass through. Various configurations are then possible, such as, the ceramic balls are enclosed in a stainless steel pouch, or they are covered with a nickel layer and then attached to an aluminum plate. The technique proposed by McDougal et al. has been criticized for its implementation difficulty and the risk inherent in the process of damaging the ceramic by thermal shock during the liquid metal coating phase. Moreover, in the casting phase, the technique recommended by McDougal et al. sometimes leads to unwanted movement of one ball relative to another. This unexpected movement affects armor effectiveness locally, and for this reason U.S. Pat. No. 4,158,338 describes a strong wall panel containing hard, and thus, nonporous ceramic particles, disposed during manufacture in a cage that holds them in position, and having holes through which is injected a liquefied elastomer whose temperature is unable to damage the ceramic particles. U.S. Pat. No. 4,534,266, which describes a method of obtaining a regular network of interconnected metal spheres that receive ceramic inserts subsequently embedded by the liquid metal during the casting stage, is also known.
Other patents, such as, for example, U.S. Pat. No. 5,194,202, U.S. Pat. No. 4,415,632, DE 3924267, and DE 3837378 describe armor having a composite layer containing a first material composed of a metal or metal alloy and a second material and characterized in that the second material is porous and in that the metal or the alloy is infiltrated into all or some of the pores of the second material.
However, such an armor cracks when struck by a projectile and when other plates made of metal, for example, are associated therewith by cementing or welding, separations occur between the plates which is detrimental to the integrity and strength of the whole or the welds break due to shear forces, leading once again to a reduction in the integrity and strength of the whole.